By the time of Shepard’s launch, the Redstone had made 69 flights with an 81 percent success rate—good enough in those days to earn it the nickname “Old Reliable.” In 1958, three months after the Sputnik launch, von Braun’s team had boosted national pride with the launch of America’s first satellite, Explorer 1, on a Juno 1. Now, with Mercury-Redstone, that team would be asked to demonstrate that an astronaut could survive a launch into space.
In 1960, the Huntsville missile group became part of NASA, and got a new name: the Marshall Space Flight Center. The Mercury capsule, meanwhile, was being developed at the agency’s Langley Research Center in Virginia, by the Space Task Group, headed by Robert Gilruth.
The Redstone and Mercury teams cooperated closely, and got along fine at a personal level. But there was an unspoken rivalry too. “The Redstone guys generally had an attitude that ‘We know what we’re doing, and it’s our launch pad,’ ” says Bryan. “The guys working on the [Mercury] capsule, from STG and McDonnell [the capsule contractor], had a lot of delays, indicating that things were new for them. Which you could understand. But our guys would double-check anything they told us, just to make sure.”
Converting a missile launcher to an astronaut-friendly rocket required about 800 modifications to the Redstone, but none was especially daunting. Some were even a step backward in terms of complexity. Instead of the highly toxic Hydyne they’d been using as fuel for longer-range Jupiters and Junos, the team switched back to alcohol, which was safer. And they used a simpler (thus less breakdown-prone) guidance control system that dated back to the V-2 days. The Redstone’s fuel tank was stretched to increase the flight time by about 20 seconds, but that too was pretty straightforward.
One key modification was adding sensors that could signal trouble and trigger an abort if some key parameter, like fuel tank pressure, was out of whack. The biggest change: placing a rocket-propelled escape tower on top of the Redstone that would pull the Mercury capsule and astronaut to safety if something went wrong early in the flight.
By November 21, 1960, the first Mercury-Redstone, MR-1, was ready for a test launch, with an empty capsule on top. The engine roared, the rocket started to rise…. then immediately settled back onto the pad. (MR-1 is still remembered as “the four-inch flight.”) With the entire space press corps watching, the escape tower blasted upward, and moments later the parachute and recovery gear came dribbling out the capsule.
In the blockhouse, the launch team was speechless. Nothing like this had ever happened. Now there was a live rocket sitting out there with 27 tons of explosive fuel. Unable to leave the blockhouse, the team considered their options. At one point, Zeiler proposed having someone shoot holes in the oxygen tank with a rifle to relieve pressure. Debus nixed the idea. Eventually they sent someone out to open up the tail of the rocket, attach a line, and slowly vent the pressure through one of the valves.
Later, they figured out what had happened. Before launch, a pad technician had been struggling to make one of the rocket’s electrical plugs fit, and had shaved off part of it. The result, on launch day, was an unintended “sneak circuit” from the ground to the rocket, milliseconds after ignition, that caused the engine to shut down. The team immediately modified the hardware to prevent another sneak circuit, and in typical Debus management style, the technician who admitted his mistake got a commendation.
A month later, MR-1A went off without a hitch. That was followed on January 31 by MR-2, with a chimpanzee named Ham inside the capsule. He was recovered safely after an ocean splashdown, but the vehicle had over-accelerated, and Debus wanted one more flawless test before putting an astronaut on board. His caution cost Shepard the honor of being the first man in space. Yuri Gagarin launched from the Soviet Union on April 12, just 19 days after the added Redstone test. The STG Mercury team, including Shepard, were angry; despite the problems on MR-2, they had wanted to go ahead with a manned flight.
The blockhouse crew generally stuck to engineering issues and left the politics and public relations to their bosses. But the pressure to succeed on the first manned launch was overwhelming, Rigell says. “To me, this launch had to go right, or we would have been…I can’t think of how low we would have been. To me, there was a tremendous amount riding on this thing.”